Stencil-printing machine



Feb. 7, 1967 E. WILFORD 3,3@2,554

STENCILPRINTING MACHINE Filed July 20, 1964 3 Sheets-Sheet 1 Feb. 7,1967 E. WILFORD STENCIL-PRINTING MACHINE Filed July 20, 1964 3SheetsSheet 2 3 Sheets-Sheet 3 Filed July 20, 1964 United States Patent3,302,564 STENCIL-PRINTING MACHINE Ernest Wilford, Crossflatts, Bingley,England, assignor to The Bradford Dyers Association Limited, Bradford,England, a British company Filed July 20, 1964, Ser. No. 383,775 Claimspriority, application Great Britain, July 19, 1963, 28,727 63 4 Claims.(Cl. 101123) In machines for the stencil-printing of textile fabrics inmore than one colour, there is a support over which the material ismoved in step-by-step fashion, a stencil which lies immediately abovethe material on the support and which has imperforated ends and acentral perforated part, and an applicator for the colouring matter.This applicator usually reciprocates over the stencil in each printingstroke, and at the end of each stroke comes to rest on an imperforatepart of the stencil. In order to allow the fabric to be moved throughone step into position for the next printing stroke, the applicator andstencil are lifted off it by lifting mechanism. In the perforated partof the stencil the openings may be completely void or may be partlyoccupied by the meshes of a screen.

The applicator may be a botttomless container, the lower edges of whichare formed by flexible lips of rubbet or similar material and thus actas squeegees in that on each stroke the trailing rubber strip forces thecolouring matter before it over the stencil and through the openings init. No great difficulty arises so long as the colouring matter is afairly viscous paste. When, however, pile fabrics and particularly pilecarpets are to be printed, I have found it necessary to use afree-flowing liquid as the colouring matter, in a bottomless container,to apply suction to the underside of the stencil and to maintainsubstantially constant the pressure difference set up across the stenciland fabric by the head of the liquid and the suction, all as describedin our US. Patent 3,129,- 442.

Now although the process and apparatus described in US. Patent 3,129,442are wholly satisfactory when the openings in the stencil are fairlylarge, it is found that there is difliculty when fine lines must beprinted and in consequence the openings in the stencil are very narrow.It then becomes desirable to apply positive pressure to the liquid. Ifsuch pressure is to be applied, it is also desirable to use another formof applicator, namely one comprising a container with a narrow bottomoutlet which lies between two squeegees that are fixed to the undersideof the bottom of the container, these squeegees acting in the same wayas those formed by flexible lips on a bottomless container. With the useof pressure in such an applicator it is possible to force the colouringliquid right through the material. However, while printing is not takingplace the pressure of the colouring liquid on the imperforate end of thestencil forces the stencil away from the bottom outlet, so that there isleakage of colouring liquid on to the stencil outside the area occupiedby the container. This drawback can be avoided by cutting off the supplyof colouring liquid at the end of each printing stroke under the controlof a timing device, but then the printing is uneven, as at the beginningof each stroke the fresh application of pressure on the colouring liquidcauses the liquid to surge downwards and in consequence the printing isheavier at the beginning of the stroke. If a timing device is employedit is impossble to control the pressure at a constant value. Fluctuatonsin pressure of as little as lb./sq. in. cause uneven printing on thecarpet.

The greater the pressure on the colouring liquid in the container, thegreater is the risk of leakage of colouring Patented Feb. '7, 1967 'iceliquid under the edge of the squeegees while the applicator is on theimperforate portion of the stencil at the end of the stroke. If leakageoccurs the colouring liquid may pass beyond the imperforate part of thestencil, and onto the screen or other perforate part, where it will besucked into the carpet by capillary action. The effect of this is thatpart of the carpet receives a preliminary quantity of colour before theprinting stroke begins, and is thus more heavily printed during thefirst portion of the printing stroke than the remainder. If the leakagebecomes really serious, it is necessary to stop the machine to preventcolouring liquid splashing over the stencil frame onto the adjacent partof the carpet.

Because of this leakage when pressure is used, as is found necessarywhen fine lines are to be printed, as operator must watch the stencilcontinuously and remove the colouring liquid by a hand scoop.

According to the invention means are provided for applying suction alongand outside each squeegee to draw away colouring liquid leaking underit.

The use of such suction is advantageous in that colouring liquid thathas leaked beneath the edges of the squeegees is removed by the suction.

Two apparatus according to the invention will now be described by way ofexample with reference to the accompanying drawings, in which:

FIGURE 1 is a diagrammatic elevation of the first apparatus;

FIGURE 2 is a diagram of an applicator above a stencil;

FIGURE 3 is a diagrammatic vertical section through the applicator;

FIGURE 4 is a longitudinal vertical section through part of a modifiedapplicator; and

FIGURES 5 and 6 are cross-sections in the lines VV and VIVI respectivelyin FIGURE 4.

FIGURE 1 shows part of a machine for printing carpets, comprising a mainframe 1 that includes a support 2 over which the carpet is moved instep-by-step fashion during printing in a series of printing stations.At each printing station there is a stencil 3 and a colour applicator 4.The stencil 3, as shown in FIGURE 2, is formed by a central screen 50which has imperforate ends 51 lying within a frame 52, and in operationthe applicator 4 comes to rest at the end of each stroke on one of theimperforate ends 51 and on the next stroke reciprocates across thestencil as shown by arrows A and comes to rest on the other imperforateend. At the end of each stroke the stencil and applicator are lifted asa whole to allow the carpet to move.

The applicator shown in FIGURE 3 has a central pressure chamber 5 forcolouring liquid lying within a suction chamber 6 both chambers beingmounted on a block 8. The block 8 carries two rubber members 9 ofinverted U-shape which extend over the whole length of the applicator,that is to say over the whole width of the machine. The inner walls 10of these members 9 constitutes squeegees lying on each side of a space11 to which passages 12 in the base of the chamber 5 and the block 8lead. Passages 13 are formed through the members 9 and the block 8 toput the suction chamber in communication with. the spaces within themembers 9.

The applicator is closed at the top except for openings to which pipes14 and 15 are connected. The pipes 14 branch from a pipe 16 which isconnected to the pressure side of a pump 17 by which colouring matter isdrawn from a container 18 and supplied to the central chamber 5 throughtubes 7 which extend upwards through the top of the suction chamber 6.The pipes 15 branch from a suction pipe 19 which is connected to asuction pump 20, the pressure side of which delivers to the container18.

In operation both the pumps 17 and 20 runs continuously so thatcolouring liquid is supplied to the central chamber 5 and suction isapplied through the suction chamber 6 to the interiors of the members 9.In consequence, colouring matter that leaks beneath the squeegee 10 andbuilds up in the spaces between the members 9 to the level of the bottomof the passage 13 is drawn away and returned to the container 18. Theouter walls of the members 9 'act as outer squeegees, and in effectbound chambers outside the squeegees constituted by the squeegees 10,the suction being applied to these chambers.

One advantage obtained is that when a wide material, for examplebroadloom carpeting, is being printed, sagging of the stencil towardsthe centre is overcome by the upward suction. In addition, if thesuction is maintained at the end of each printing stroke it exerts anupward lift of the stencil which causes this to remain in firm contactwith the squeegees and thus to prevent leakage when the stencil andapplicator are lifted.

The applicator shown in FIGURE 3 may be used with advantage wheneverpositive pressure on the liquid is desirable.

When a deep pile carpet is being printed in a pattern that includes finelines, it is found that neither the use of the combined gravity head andsuction nor of positive pressure alone gives the best results. Rather itis desirable to effect the printing in two stages. In the first of thesestages free-flowing colouring liquid is applied to the stencil undergravity while suction is applied to the underside of the fabric and inthe second stage further colouring liquid is applied to the stencilunder positive pressure. If the line is very narrow, the printing in thefirst stage will adequately colour the top of the pile, but thecolouring liquid will tend not to colour the base of the pile uniformly.Rather, the colour extends downwards in decreasing width. When thefurther colouring liquid is applied under pressure in a second stage,the pile becomes substantially uniformly coloured throughout its wholedepth over the desired narrow line.

A pattern to be printed on a carpet often is formed by relatively largeareas of different colours, for example of seven different colours, andfine lines of another colour. In order to print such a carpet there maybe eight printing stations, one for each colour, and at each at whichthe areas are relatively large the printing may be effected with theliquid under a gravity head and the application of suction below theperforated support over which the carpet moves. In the remaining stationthe printing may be effected in two stages with the use of an applicatoras shown in FIGURES 4 to 6 and with the application of suction to theunderside of the carpet.

The applicator of FIGS. 46 is a box-like structure having end walls 21and side walls 22. An assembly 23 extends from one end wall to the otherwithin the side walls and is composed of a top header section 24, amiddle chamber section 25 and a bottom printing section 26. The topheader section 24 is bounded at the underside by a horizontal partition27 and is divided longitudinally by vertical partitions 47 intoalternating suction and supply pipes 30 and 31 are connected. There 'arethree suction chambers 28 and two pressure chambers 29. Below thepartition 27 the middle section 25 is divided by vertical partitions 48into a further pressure chamber 54 and two lateral suction chambers 32and 33. Passages 34 are made through the partition 27 to put both thepressure chambers 29 in communication with the chamber 54, and passages49 are made in the same partition to put all the suction chambers .28 incommunication with both the suction chambers 32 and 33. A nozzle 35 liesbeneath the bottom of the chamber 54 and receives colouring liquid fromthis chamber through opening 36. This nozzle 35 lies in a space 37between two longitudinal members 38, on the undersides of which thereare doublelipped squeegees 39.

The assembly 23 is spaced away from the long side walls 22 to formchambers 41 and 42 which communicate with the atmosphere throughpassages 43. Squeegees 44 are clamped to the side walls 22 by plates 50and form the lower boundaries of the chambers 41 and 42, whichcommunicate with the chambers 32 and 33 through passages 45. Thesqueegees 44 are suitably shaped by bevelling the lips to ensure thebest possible contact with the stencil at the end of each stroke, andwhile the stencil is lifted. In this applicator, it will be seen, thesuction is applied to the chambers 41 and 42, which are bounded bysqueegees but which are also open to atmosphere, with the result thatcolouring liquid can build up in them to the level of the bottoms of thepassages 43 when printing is not taking place.

Trunnions 46 are provided on the end walls for engagement by liftingmechanism not shown.

In operation, suction is applied to the underside of the perforatedsupport 2 through a suction box 53, the top of which is formed by thesupport 2, as shown in FIG- URE 1. This suction is continuously appliedthroughout the whole of each printing stroke, but is destroyed andreplaced by positive pressure at the end of each stroke to enable thecarpet or other fabric easily to be moved through one step to bring afresh length into each printing station.

The pressure on the colouring liquid in the chamber 54 forces it beneaththe squeegees 39 into the chambers 41 and 42, but as these are not underpressure but actually are under suction there is little or no tendencyfor the colouring liquid to leak past the squeegees 44. In fact duringthe printing the suction exerted through the passages 45 is largelysatisfied by air entering through the passages 43. At the end of eachprinting stroke colouring liquid passes into and tends to build up inthe chambers 41 and 42, but the extent to which it can build up islimited, since when it reaches the level of the bottoms of the passages45, the suction ceases to be satisfied by air and is wholly exerted onthe colouring liquid. This liquid is thus drawn up into the suctionchambers above it, and at the beginning of each printing stroke there isa constant head of colouring liquid in each of the chambers 41 and 42.As the printing stroke proceeds, colouring liquid flows from the leadingchamber 41 or 42 as the case may be through the openings in the stencilinto the carpet. Simultaneously the amount of suction exerted on eachopening of the stencil is reduced, as explained in US. Patent 3,129,442,and initial printing therefore takes place under a substantiallyconstant pressure difference. Printing further takes place in a secondstage as the space 37 comes over each opening in the stencil, and asexplained above this is found to produce more uniform printing throughvery narrow openings in the stencil than if printing takes place in asingle stage.

If desired, printing by an applicator as shown in FIG- URES 46 may becarried out without the use of suction under the fabric. In this case,printing is effected by the colouring liquid in the outer chambers 41and 42 under gravity alone, and continued by the liquid in the centrespace 37 under pressure.

The invention enables uniform printing to be effected, without the useof timing devices for cutting off the supply of colouring liquid.

I claim:

1. A stencil-printing machine for pile fabric comprising a stencilhaving imperforate ends and a central perforated part, a support for thefabric passing beneath said stencil, and applicator means mounted forreciprocating movement over said stencil and having a bottom openingextending over the entire length of said applicator means for the supplyof free-flowing coloring liquid under pressure to said stencil, a pairof inner squeegees secured to said applicators means on opposite sidesof said opening and adapted to bear on said stencil, a pair of outerSqueegees secured to said applicator means and spaced from said innersqueegees on opposite sides thereof to define bounding chambersextending over the entire length of said applicator means outside saidinner Squeegees, and means for applying suction to said chambers to drawaway coloring liquid leaking under said inner squeegees into saidchambers.

2. A stencil-printing machine according to claim 1 wherein saidapplicator means further comprises a central pressure chamber flanked bytwo suction chambers and flexible means connected to the tops of saidchambers for supplying liquid to the pressure chambers and suction tothe suction chambers.

3. A stencil-printing machine according to claim 1 wherein saidapplicator means further comprises a central pressure chamber lyingwithin a suction chamber and flexible means connected to the tops ofsaid chambers for supporting liquid to the pressure chamber and suctionto the suction chambers.

4. A stencil-printing machine according to claim 1 in which each outerbounding chamber is open to atmosphere to allow colouring liquid tobuild up in it when printing is not taking place.

References Cited by the Examiner UNITED STATES PATENTS FOREIGN PATENTS9/ 1956 Belgium. 5/ 193 2 Great Britain. 4/ 195 2 Germany.

ROBERT E. PULFR EY, Primary Examiner.

H. P. EWELL, Assistant Examiner.

1. A STENCIL-PRINTING MACHINE FOR PILE FABRIC COMPRISING A STENCILHAVING IMPERFORATE ENDS AND A CENTRAL PERFORATED PART, A SUPPORT FOR THEFABRIC PASSING BENEATH SAID STENCIL, AND APPLICATOR MEANS MOUNTED FORRECIPROCATING MOVEMENT OVER SAID STENCIL AND HAVING A BOTTOM OPENINGEXTENDING OVER THE ENTIRE LENGTH OF SAID APPLICATOR MEANS FOR THE SUPPLYOF FREE-FLOWING COLORING LIQUID UNDER PRESSURE TO SAID STENCIL, A PAIROF INNER SQUEEGEES SECURED TO SAID APPLICATORS MEANS ON OPPOSITE SIDESOF SAID OPENING AND ADAPTED TO BEAR ON SAID STENCIL, A PAIR OF OUTERSQUEEGEES SECURED TO SAID APPLICATOR MEANS AND SPACED FROM SAID INNERSQUEEGEES ON OPPOSITE SIDES THEREOF TO DEFINE BOUNDING CHAMBERSEXTENDING OVER THE ENTIRE LENGTH OF SAID APPLICATOR MEANS OUTSIDE SAIDINNER SQUEEGEES, AND MEANS FOR APPLYING SUCTION TO SAID INNER SQUEEGEES,AND AWAY COLORING LIQUID LEAKING UNDER SAID INNER SQUEEGEES INTO SAIDCHAMBERS.